A STUDY OF DENIAL ARCH FORM IN NORMAL OCCLUSION

정상교합의 치열궁형태에 관한 연구

This study was to investigate the fitness of the dental arch line to the parabola, and to estimate correlation between the parabola and some ratios of the dental arch measurements. The sample was consisted of the 64 plaster casts showing normal occlusion which was taken from males and females of Korea, aging from 15 to 18 years. The photos of occlusal surface of the plaster casts were taken, and 38 landmarks on the film were selected. The 3 dental arch lines on each dental arch were imaged. One is the dental arch line passing the points of the most buccal surfaces of the teeth, another is that passing the buccal cusp tips of the posterior teeth and the incisal edges, and the other is that passing the midpoints of the teeth. The landmarks on the film were digitized, and measurements and statistics were performed by the IBM computer. The results were as follows; 1. The fitness of the dental arch to the parabola was very good. The fitness of thor upper dental arch was above $91\%$, and that of the lower dental arch was $93\%$. 2. The dental arch line passing the points of the most buccal surfaces of teeth was best fit to the parabola, the buccal cusp tip arch line and the midpoint arch line in order. 3. Correlation between the ratio of oblique molar dental height to molar width and the parabola was very high. 4. The ratio of oblique molar dental height to molar width was devided into 4 groups by the quartiles, and mean parabolic equations and curves were calculated and drawn.